Traumatic head and neck injury is the leading cause of death for children in the United States (15,000 each year) and permanently disables close to 150,000 more children annually. These statistics persist in spite of interventions like advanced safety systems in cars and new safety gear and surfaces for sports and playgrounds. Unfortunately, these interventions have been developed largely in the absence of child biomechanical data for the head and neck, relying on geometrical scaling of the adult to child. This strategy is flawed particularly for the head and neck due to their differential allometry-head circumference of a 4- year-old is 90% of its adult value while the neck circumference does not approach 90% of adult until age 14. We have, therefore, engaged in an effort to characterize and simulate head and neck biomechanics during maturation. Through a better understanding of child neck mechanics during these changes, emergency medical services such as patient extraction, transport, and diagnosis can be performed without further exacerbation of child head and neck injuries. Further, knowledge of the response of the child head and neck to injurious scenarios will facilitate the prevention of these injuries. The objective of this research is to characterize the developmental growth trajectories of neck muscles and employ these data in a head and neck computational model able to address emergency medical services and injury prevention in children. Specifically, this research effort will begin with a human subject experiment examining neck muscle mechanics across the developmental spectrum (4-to-23 years). The peak and endurance mechanics will be measured and correlated with muscle biopotentials (EMG), subject anthropometry, age, and sex (specific aim 1). These data and our previous work will support the development and validation of a series of child musculoskeletal models to examine parametric issues affecting child head and neck injury (specific aim 2). These models will be able to assess current automotive, sport, and emergency care injury prevention strategies and expose improvements (specific aim 3). The clinical import of this work lies in modifications for emergency medical extraction, transport, and diagnosis of the injured child and advancements in child safety devices all afforded by an improved understanding of pediatric musculoskeletal neck mechanics.